The Messenger of Allah ﷺ used to say seven takbirs in the first rakah and five in the second during the prayers of Eid al-Fitr and Eid al-Adha.
حدثنا قتيبة حدثنا ابن لهيعة عن عقيل عن ابن شهاب عن عروة
أن رسول الله ﷺ كان يكبر في الفطر والأضحى في الأولى سبع تكبيرات وفي الثانية خمسا
[Hasan]. Ibn Majah narrated it in Iqamat as-Salawat, chapter on how many times the imam says the takbir in the prayer of the two Eids, hadith no. 1280, from the hadith of Ibn Lahia, with this wording. The hadith has corroborating narrations, see hadith no. 1151.